1. Field of the Invention
The present invention relates to hand held optical reading devices, and is directed more particularly to a hand held optical reading device configured to be controlled with use of a local host processor.
2. Description of the Prior Art
One dimensional optical bar code readers are well known in the art. Examples of such readers include readers of the SCANTEAM(copyright) 3000 Series manufactured by Welch Allyn, Inc. Such readers include processing circuits that are able to read one dimensional (1D) linear bar code symbologies, such as the UPC/EAN code, Code 39, etc., that are widely used in supermarkets. Such 1D linear symbologies are characterized by data that is encoded along a single axis, in the widths of bars and spaces, so that such symbols can be read from a single scan along that axis, provided that the symbol is imaged with a sufficiently high resolution along that axis.
In order to allow the encoding of larger amounts of data in a single bar code symbol, a number of 1D stacked bar code symbologies have been developed, including Code 49, as described in U.S. Pat. No. 4,794,239 (Allais), and PDF417, as described in U.S. Pat. No. 5,340,786 (Pavlidis, et al). Stacked symbols partition the encoded data into multiple rows, each including a respective 1 Dbar code pattern, all or most all of which must be scanned and decoded, then linked together to form a complete message. Scanning still requires relatively high resolution in one dimension only, but multiple linear scans are needed to read the whole symbol.
A third class of bar code symbologies, known as two dimensional (2D) matrix symbologies, have been developed which offer orientation-free scanning and greater data densities and capacities than their 1D counterparts. 2D matrix codes encode data as dark or light data elements within a regular polygonal matrix, accompanied by graphical finder, orientation and reference structures. When scanning 2D matrix codes, the horizontal and vertical relationships of the data elements are recorded with about equal resolution.
In order to avoid having to use different types of optical readers to read these different types of bar code symbols, it is desirable to have an optical reader that is able to read symbols of any of these types, including their various subtypes, interchangeably and automatically. More particularly, it is desirable to have an optical reader that is able to read all three of the above-mentioned types of bar code symbols, without human intervention, i.e., automatically. This in turn, requires that the reader have the ability to automatically discriminate between and decode bar code symbols, based only on information read from the symbol itself. Readers that have this ability are referred to as xe2x80x9cautodiscriminatingxe2x80x9d or having an xe2x80x9cautodiscriminationxe2x80x9d capability.
If an autodiscriminating reader is able to read only 1D bar code symbols (including their various subtypes), it may be said to have a 1D autodiscrimination capability. Similarly, if it is able to read only 2D bar code symbols, it may be said to have a 2D autodiscrimination capability. If it is able to read both 1D and 2D bar code symbols interchangeably, it may be said to have a 1D/2D autodiscrimination capability. Often, however, a reader is said to have a 1D/2D autodiscrimination capability even if it is unable to discriminate between and decode 1D stacked bar code symbols.
Optical readers that are capable of 1D autodiscrimination are well known in the art. An early example of such a reader is the Welch Allyn SCANTEAM(copyright) 3000, manufactured by Welch Allyn, Inc.
Optical readers, particularly hand held optical readers, that are capable of 1D/2D autodiscrimination are less well known in the art, since 2D matrix symbologies are relatively recent developments. One example of a hand held reader of this type which is based on the use of an asynchronously moving 1D image sensor, is described in copending, commonly assigned U.S. Pat. No. 5,773,806, which application is hereby expressly incorporated herein by reference. Another example of a hand held reader of this type which is based on the use of a stationary 2D image sensor, is described in copending, commonly assigned U.S. patent application Ser. No. 08/914,833, which is also hereby expressly incorporated herein by reference.
Optical readers, whether of the stationary or movable type, usually operate at a fixed scanning rate. This means that the readers are designed to complete some fixed number of scans during a given amount of time. This scanning rate generally has a value that is between 30 and 200 scans/sec for 1D readers. In such readers, the results of successive scans are decoded in the order of their occurrence.
Prior art optical readers operate relatively satisfactorily under conditions in which the data throughput rate, or rate at which data is scanned and decoded, is relatively low. If, for example, the scanning rate is relatively low and/or the data content of the bar code or other symbol is relatively small, i.e., the scanner is operating under a relatively light decoding load, the decoding phase of the reading process can be completed between successive scans. Under these conditions scan data can be accurately decoded without difficulty.
Readers of the above-described type have the disadvantage that, if they are operated under relatively heavy decoding loads, i.e., are required to rapidly scan symbols that have a relatively-high data content, the tracking relationship or synchronism between the scanning and decoding phases of the reading process will break down. This is because under heavy decoding loads the decoding phase of a read operation takes longer than the-scanning phase thereof, causing the decoding operation to lag behind the scanning operation. While this time lag can be dealt with for brief periods by storing the results of successive scans in a scan memory and decoding the results of those scans in the order of their occurrence when the decoder becomes available, it cannot be dealt with in this way for long. This is because, however large the scan memory, it will eventually overflow and result in a loss of scan data.
One set of solutions to the problem of maintaining the desired tracking relationship between the scanning and decoding phases of the reading process is described in previously mentioned copending U.S. patent application Ser. No. 08/914,833. Another set of solutions to the problem of maintaining the desired tracking relationship between the scanning and decoding phases of the reading process is described in U.S. Pat. No. 5,463,214, which issued on the parent application of the last mentioned copending patent application.
Generally speaking, the latter of these two sets of solutions to the above-discussed tracking problem involves the suspension of scanning for brief periods in order to assure that the scanning process does not pull too far ahead of the decoding process. The former of these two sets of solutions to the above-discussed tracking problem, on the other hand, involves the skipping over of one or more sets of scan data, in favor of more current scan data, if and to the extent necessary for tracking purposes, in combination with the use of two or more scan data memories to minimize the quantity of scan data that is skipped.
Prior to the present invention, no consideration has been given to accomplishing scan-decode tracking in conjunction with 1D/2D autodiscrimination, i.e., as cooperating parts of a single coordinated process. This is in spite of the fact that the 1D/2D autodiscrimination is known to involve heavy decoding loads of the type that give rise to tracking problems. Thus, a need has existed for an optical reader that combines a powerful tracking capability with a powerful 1D/2D autodiscrimination capability.
As new and/or improved 1D and 2D bar code symbologies, and as additional 1D and 2D decoding programs come into widespread use, previously built optical readers may or may not be able to operate therewith. To the extent that they cannot operate therewith, such previously built optical readers will become increasingly obsolete and unusable.
Prior to the present invention, the problem of updating optical readers to accommodate new bar code symbologies and/or new decoding programs has been dealt with by manually reprogramming the same. One approach to accomplishing this reprogramming is to reprogram a reader locally, i.e., on-site, by, for example, replacing a ROM chip. Another approach to accomplishing this reprogramming is to return it to the manufacturer or his service representative for off-site reprogramming. Because of the expense of the former and the time delays of the latter, neither of these approaches may be practical or economical.
The above-described problem is compounded by the fact that, if an optical reader is not equipped to operate as a tracking reader, it may not be possible to reprogram it to use an autodiscrimination program that is designed to be executed in conjunction with tracking. This is because the autodiscrimination program may include steps that require the tracking feature to prevent data from overflowing the scan memory and being lost. Alternatively, the scan rate may be decreased, although this reduction will adversely affect performance when low data content symbols are read. Thus, a need has existed for an optical reader that can be reprogrammed economically in a way that allows it to realize the full benefit of the 1D/2D autodiscrimination and tracking features, among others.
In accordance with the present invention, there is provided an optical scanning and decoding apparatus and method, suitable for use with bar code readers, bar code scanning engines, and portable data terminals (PDTs), which combines improved scanning-decoding and autodiscrimination features in the context of an apparatus and method which also provides improved menuing and reprogramming features.
In accordance with the menuing feature of the invention, there is provided an improved apparatus and method which enables a user to determine the current operating mode of an optical reading apparatus, and to rapidly and conveniently change that operating mode to optimize it for operation under then current conditions. The menuing feature, for example, enables the user, via a machine readable table of pre-recorded menu symbols, to command the reader to communicate with a host processor using one of a number of protocols, to command the reader to format the decoded output according to host processor requirements, or to command the reader to report to the host processor any of a plurality of types of information about the current operating state of the reader, such as the version of software then being used, the code options that are then being used, and even a complete listing of the reader""s parameter table. If a suitable printer is available, the complete status of a first reader may be output as a machine readable menu symbol that other, similarly equipped readers may read and use to reconfigure themselves for operation in the same manner as the first reader.
In accordance with the reprogramming feature of the invention, there is provided an improved apparatus and method by which an optical reader may be reprogrammed from a source external to the reading apparatus, with or without the participation of a user. This external source may be either on-site, i.e., located at the same local facility as the reader, or off-site, i.e., located at a remote facility that is coupled to the local facility only via a transmission line or computer network. When actuated, the reprogramming feature enables a reader to reprogram itself, either in whole or in part, and thereby become able to operate with operating software of the latest type. Depending on the application, the reprogramming of the reader may be initiated either by a host processor external to the reader, as by a command issued via the reader""s communication port, or by a user initiated command issued as a part of the above-mentioned menuing process.
In accordance with another aspect of the reprogramming feature, a local host processor may be configured to carry out reprogramming of an optical reader or another type of portable data terminal. In a reprogramming subroutine according to the invention a local host processor can be made, at the selection of a user, to replace an entire main program and parameter table of a reader, or else one of either a main program or a parameter table of an operating program individually.
In accordance with another subprogram of a local host processor, the local host processor can be made to edit a parameter table. When this subprogram is selected the user may either edit the parameter table that is stored in a memory device of the reader or else edit a parameter table stored in a memory device in communication with the local host processor. After editing, the user may write the edited parameter table to the reader""s memory device, write the edited parameter to the a bulk storage device for later use, or print or display the edited parameter table. In accordance with another aspect of the invention, an optical reader of the invention may be made to receive a component control instruction from a host processor which is transmitted in response to a user input command to remotely control an optical reader. In accordance with this aspect of the invention, the optical reader is made to execute a component control instruction substantially on receipt thereof. In one embodiment, execution by an optical reader of a component control instruction has the same effect as a reader trigger being manually pulled.
In accordance with the present invention, there is also provided an optical scanning and decoding apparatus and method which includes improved scanning-decoding and autodiscrimination features, either or both of which may be used in conjunction with, and/or under the control of, the above-described menuing and reprogramming features. In other words, the autodiscrimination feature of the invention is made available to the user on a menu selectable or reprogrammable basis to speed up and/or update the decoding phase of the scanning and decoding process. Together, these features enable the reading apparatus of the invention to read and decode a wide range of optically encoded data symbols at an improved data throughput rate.
When a reader is one in which the scan engine cannot be readily started and stopped, or in which such starts and stops impose unacceptable delays or produce user perceptible flicker, the present invention preferably operates in one of the tracking relationships described in previously mentioned copending application Ser. No. 08/914,833. One of these tracking relationships is a Skip Scan tracking relationship in which the results of one or more scans may be skipped over entirely in favor of more recently produced scan results. Another is a Decode On Demand tracking relationship in which decoding is suspended briefly as necessary to allow a scan then in progress to be completed. The latter relationship is ordinarily not preferred, but is still useful when the reader is such that its scan memory is able to store only two complete blocks of scan data.
When the reader is one in which the scan engine can readily be stopped, the present invention may operate in the tracking relationship described in previously mentioned U.S. Pat. No. 5,463,214. With this, xe2x80x9cScan On Demandxe2x80x9d tracking relationship, scanning is suspended briefly as necessary to prevent scanning and decoding from becoming uncorrelated with one another.
In the preferred embodiment, the reader includes an algorithm that is able to accommodate any of the above-described scanning-decoding relationships, among others. Which of them is actually used will vary from reader to reader depending upon the size and type of memory and the type of scan engine used thereby, and may be changed from time to time.
The present invention also contemplates and provides for at least one scanning-decoding relationship which does not fall within the meaning of the above-defined tracking relationships. One of these non-tracking relationships is a xe2x80x9cOne Shotxe2x80x9d relationship or mode in which a single scan is followed by a single decoding attempt and then a stoppage. Such scanning-decoding events may be initiated by respective single actuations of a manual trigger. Because of its inherently discontinuous nature, the use of the One Shot mode implies the non-use of any of the above-mentioned tracking modes.
Two other such scanning-decoding relationships are referred to herein as the xe2x80x9cRepeat Until Donexe2x80x9d relationship or mode and the xe2x80x9cRepeat Until Stoppedxe2x80x9d relationship or mode. With the Repeat Until Done relationship, scanning and decoding operations follow one after another until a successful decode occurs, and are then discontinued. With the Repeat Until Stopped relationship, scanning and decoding operations follow one after another and continue, even after sets of decoded data are stored or output, until instructed to stop by the release of the trigger or by the readersxe2x80x2 program. Because of their repetitive nature, the use of Repeat Until Done and Repeat Until Stopped modes are usable both in conjunction with the above-described tracking modes and independently of those tracking modes. As a result, the Repeat Until Done and Repeat Until Stopped modes may be implemented as user selectable non-tracking relationships or as tracking relationships.
In embodiments that use the auto discrimination feature of the invention, there is provided a method and apparatus by which a plurality of different symbols of a multiplicity of different types may be scanned and decoded in a manner that is optimized for a particular application, on either a menu selectable or a reprogrammable basis. When all of the symbols to be autodiscriminated are known to be 1D symbols, for example, the data throughput rate may be increased by structuring the autodiscrimination feature of the invention so that no attempt is made to decode 2D symbols, or vice versa. When, on the other hand, the symbols to be autodiscriminated are known to all be of (or all not to be of) a few types, whether 1D or 2D, the data throughput rate may be increased by structuring the autodiscrimination feature so that all but a few (or only a few) 1D and/or 2D symbologies are disabled, i.e., so that no attempt is made to decode them. Other possible autodiscrimination options include not decoding or not outputting data for symbols that encode messages that are too long or too short to be of interest in a particular application. In accordance with the invention, any of these options may be chosen and changed as necessary to achieve the highest possible data throughput rate.
Because of the large number of different combinations of distinct operational states that are made possible thereby, the apparatus and method of the invention will be seen to have a protean quality that not only makes it usable in a large number of different applications, but also enables it to continue to remain so usable as new functions, new bar code symbologies and new and updated decoding programs are developed in the future.